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Abstract:

An angled dental shaft receptacle is provided for operating rotating
instruments with an angled shaft. The angled shaft receptacle has a
driver pin, and the driver pin is connected to the angled shaft of the
instrument by a planar contact during operation. The rotating instrument
is preferably a dental instrument.

Claims:

1. An angled shaft receptacle for operating rotating instruments having an
angled shaft, the angled shaft receptacle comprising a driver pin,
wherein the driver pin is connectable to the angled shaft for operation
by a planar contact, and wherein the planar contact, which is formed by
the driver with the angled shaft, lies in a range defined by Hooke's Law.

2. The angled shaft receptacle according to claim 1, wherein the angled
shaft receptacle is operable by a motor or manually for operation of the
rotating instrument.

3. The angled shaft receptacle according to claim 1, wherein the driver
pin has a constant radius at a force-transmitting surface.

4. The angled shaft receptacle according to claim 1, wherein the driver
pin has a variable radius at a force-transmitting surface.

5. The angled shaft receptacle according to claim 1, wherein the driver
pin has a combination of surfaces and radii of variable type on a
force-transmitting surface.

6. The angled shaft receptacle according to claim 1, wherein a supporting
thrust bearing is present in the angled shaft receptacle on a side
opposite the driver pin.

7. The angled shaft receptacle according to claim 1, wherein the rotating
instrument is a dental instrument.

Description:

BACKGROUND OF THE INVENTION

[0001]Dental instruments of all types, which are provided for use as
rotating instruments in an angled piece, also conceivable as an angled
shaft receptacle, have a specially shaped shaft, called an angled piece
connection or also angled shaft. This connection has been standardized
for rotating tools and is manufactured worldwide in specified dimensions
and tolerances. It is used equally for tools with high rotational speeds
and small torques and with high torques and low rotational speeds, for
example drills, enhancers, cutting attachments, thread cutters,
counterbores, insertion instruments for implants, etc.

[0002]The rotating tools can be set and used with this type of connection,
not only in motor-driven angled pieces, but also in manually-activated
handles or adapters. The angled shaft is a critical interface for the use
of nearly all types of dental tools.

[0003]This known convention for the structural shape of the
force-transmitting connection on the shaft of the instrument (e.g., a
drill) does not take into account the torques that are possible today and
that are in some places necessary in dental instrumentation. The
counterpiece for the force transmission in the adapter or angled piece is
often not in a position for guaranteeing an optimum force transmission.
Similarly, it does not take into account modern requirements for higher
torques. Mostly, simple metal sheets are stamped for angled pieces, in
order to obtain a reverse contour for the angled shaft. These metal
sheets are then used as torque drivers and transmit the torque to the
shaft via a contact region. For angled pieces in the form of hand
adapters or shaft extenders, for the most part, pins are turned with a
driver finger, which then similarly transmit the force to the shaft via a
contact surface. All of these force-transmitting surfaces are shaped in
such a way that a linear contact surface is formed between the two parts.

[0004]It has been shown that for high torques, the dental instrument or
the angled piece, or both are damaged. The two components can seize or
one part of the assembly can be destroyed. This is assisted by a
currently used linear contact of the parts, because these are plastically
deformed by high forces.

[0005]The tolerances between the angled shaft and the driver pin of the
angled piece always lead to twisting between the two force-transmitting
surfaces. This is bigger or smaller according to the tolerances of the
two components and leads to a greater or smaller angle difference of the
two force-transmitting surfaces. This leads to the fact that the two
surfaces come into contact with each other only in a linear contact at
the outer edge of the shaft. This linear contact surface at the outer
edge of the angled shaft is plastically deformed according to the
calculable rules of Hertzian pressure and forms newly shaped contact
surfaces, until the surface pressure formed by the force transmission
falls below the plastic deformation limit Rp 0.2. With the torque
necessary under some circumstances for supplying implants or the
specified tightening of prosthetic screws with a minimum torque
prescribed by the manufacturer, force levels are reached which, in the
current structural solution of the contact surface, lead to loading
significantly above the plastic deformation limit of typical materials
for rotating tools. Clear and permanent deformations in the form of
bevels and burrs are formed on the outside shaft edge on the
force-transmitting surfaces.

[0006]From the formation of these deformation surfaces changes in the
diameter of the shaft geometry can result, so that the instrument seizes
in the angled piece or a damaging reverse coupling to the structure of
the angled piece is created. The deformation of the angled shaft can also
lead to the functional failure of the connection.

[0007]An economically less meaningful path is to reduce the manufacturing
tolerances. However, according to current technical solutions, it is the
only possibility for minimizing this effect. Furthermore, the use of
higher-strength materials with an increased expansion limit can shift the
effect of deformation to higher torques. This is likewise a
non-economical path in terms of manufacturing, because the production of
dental tools in principle becomes more expensive. A structural change is
not in line with the market, at least for the shaft connections, due to
the decades-long standardization of the angled shaft dimensions. The goal
must be to achieve an improvement with changes to the construction of the
angled piece and its geometry of the driver pin.

BRIEF SUMMARY OF THE INVENTION

[0008]Therefore, the problem of the invention is to provide an angled
shaft receptacle for the operation of dental instruments or an angled
shaft in an angled piece or hand adapter, which allows improved
transmission of torques.

[0009]The angled shaft receptacle of an angled dental piece according to
the invention for rotating dental instruments, wherein the angled shaft
receptacle has a driver pin, provides that the driver pin and the angled
shaft are always connected in the angled shaft receptacle by a planar
contact during the operation of the angled piece.

[0010]In this way, only the angled shaft receptacle (angled piece) is
changed structurally, whereby the prevailing standards for manufacturing
dental instruments or their angled shaft geometry are still totally taken
into account. The transmission of significantly higher torques is thereby
permitted free from damage. The possibilities for using this universal
connection system for dental tools is therefore significantly increased
and made significantly more reliable in use.

[0011]Advantageously, the angled piece is driven by a motor or manually.

[0012]An advantageous embodiment of the invention provides that the planar
contact, which is formed by the driver of the angled shaft receptacle
with the angled shaft and which is necessary for the force transmission,
generates only deformations of the contact surfaces in the Hooke's Law
range. The deformations of the contact surfaces are thus purely elastic;
the material is thus subjected to no plastic deformation.

[0013]The planar contact must be constructed in such a way that, for all
of the resulting tolerance pairings, a surface is created, which fulfills
the criterion:

[0014] contact surface≦Rp 0.2.

[0015]For determining this condition, the principles of Hertzian pressure
apply. These principles allow a calculation of various geometric body
contacts and allow the surface pressures created in the material to be
estimated. A material, which is loaded below the plastic deformation
limit, is deformed only reversibly or elastically and assumes its
original shape again after loading.

[0016]Thus, independent of the manufacturing tolerances, a unit
functioning uniformly free from damage can always be provided.

[0017]Advantageously, the driver pin has a constant radius at the
force-transmitting surface.

[0018]In a preferred embodiment, the invention provides that the driver
pin has a variable radius at the force-transmitting surface. This
variable radius can have a special functional relationship.

[0019]It has been shown that it is advantageous if the driver pin has a
combination of surfaces and radii of variable type at the
force-transmitting surface.

[0020]According to the invention, the driver of the angled shaft
receptacle (angled piece) should be shaped in such a way that the contact
position always consists of the flat surface of the angled shaft and a
curved surface of the driver of the receptacle, independent of the
tolerances of the components.

[0021]Advantageously, a supporting thrust bearing is provided on the side
opposite the driver pin.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0022]The foregoing summary, as well as the following detailed description
of the invention, will be better understood when read in conjunction with
the appended drawings. For the purpose of illustrating the invention,
there are shown in the drawings embodiments which are presently
preferred. It should be understood, however, that the invention is not
limited to the precise arrangements and instrumentalities shown. In the
drawings:

[0023]FIG. 1a is a side view of an angled shaft according to the prior
art;

[0024]FIG. 1b is an end view of the angled shaft according to FIG. 1a;

[0025]FIG. 2a is an end view of a driver pin in an angled piece (angled
shaft receptacle) according to the prior art;

[0026]FIG. 2b is a sectional side view of a driver pin in an angled piece
(angled shaft receptacle) according to FIG. 2a;

[0027]FIGS. 3a and 3b are end views of are end views of connections of the
angled shaft and the angled piece with a driver pin according to the
prior art;

[0028]FIGS. 4a to 4d are end views of a driver pin in an angled piece
according to various embodiments of the invention; and

[0029]FIGS. 5a and 5b are end views of a connection of the angled shaft
and the angled piece with a driver pin according to an embodiment of the
invention in unloaded and torsion loaded conditions, respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0030]FIG. 1a shows an angled shaft 1 of the prior art, as provided for
rotating instruments. Seen here is an end surface, which is used for
force transmission. The end surface has a height 10 of approximately 1.8
mm. To achieve an ideal force transmission and to allow use in standard
devices, the angled shaft 1 is constructed in such a way that the total
diameter 16 of the angled shaft 1 equals approximately 2.35 mm. As shown
in FIG. 1b, the distance 12 between the center of the end surface and the
outer edge equals 0.625 mm at the smallest point.

[0031]FIGS. 2a and 2b show a driver pin 18 in an angled piece 14, in which
the angled shaft 1 can be inserted. The driver pin 18 is here constructed
as a counterpiece to the angled shaft 1 and its end surface with height
10 and naturally has a clearance fit, so that an air gap is produced
between the two surfaces. The greater the play, the easier the instrument
can be inserted, but the greater the tendency for jamming. Not shown is a
lock, which holds the angled shaft 1 in its position in the angled piece
14. The edge of the driver pin 18 has a construction lying straight with
the angled shaft.

[0032]FIG. 3a shows an end view of the connection of the angled shaft 1
and the angled piece 14 with a driver pin 18 according to the prior art,
in an unloaded state. Here, the edge of driver pin 18 is straight and
contacts the angled shaft 1 and its upper end surface with its entire
surface. Here, the typical linear contact is represented in FIG. 3b under
a load, which can lead to damage at the outer edge of the angled shaft 1.

[0033]FIGS. 4a to 4d show end views of a driver pin 18 in an angled piece
14 according to embodiments of the invention. Shown are several
possibilities for the configuration of the geometry of the driver pin, so
that the contact surface for the angled shaft 1 and the end surface of
the instrument is always formed in a planar contact position. The
distance 12 between the center of the end surface and the outer edge
equals approximately 0.625 mm. It can be seen clearly that the contact
edge of the driver pin 18 in the angled piece 14 is slightly curved. By
this curvature of the edge, good durability and stability of the dental
instrument are achieved, because this curvature allows the planar contact
to be formed independently of angle. It always leads to a planar contact
without linear contact. Here, the curvature of the edge of the driver pin
18 can have different magnitudes of curvature and can optionally have
section(s) t which are even straight, as shown, for example, in FIG. 4c.

[0034]In FIG. 5a, an unloaded connection of the angled shaft 1 and the
angled piece 14 is shown in end view with a driver pin 18 according to an
embodiment of the invention. An embodiment according to the invention is
shown, in which a planar force transmission is realized with the help of
a constant radius. In FIG. 5b the planar contact is represented under
torsion loading, which is formed at a contact between the surface of the
angled shaft 1 and the curvature of the driver pin 18.

[0035]It will be appreciated by those skilled in the art that changes
could be made to the embodiments described above without departing from
the broad inventive concept thereof. It is understood, therefore, that
this invention is not limited to the particular embodiments disclosed,
but it is intended to cover modifications within the spirit and scope of
the present invention as defined by the appended claims.